Analysis of a Long-term Experiment with Repeated-measurement Models

Long‐term experiments are a classical case of repeated measurements. Traits are measured on the same experimental unit over many years so that correlations arise between the observations made on the same plot in consecutive years. This paper describes the analysis of a three‐crop‐rotation long‐term experiment. We analysed the yields of the crops and the organic carbon content in the topsoil over 30 consecutive years. Several variance–covariance approaches are discussed and the trait‐specific best fit is interpreted. Mixed models are used to describe the structure of the experiment. Both yields and soil organic carbon show a more or less pronounced variance heterogeneity. Especially for yields, the heterogeneity of cycles and years is dominant. The consideration of correlations results in a better model fit in all cases.     

Effect of milk sampling techniques on milk composition, bacterial contamination, viability and functions of resident cells in milk.

Three different milk sampling techniques were evaluated during milk sampling: a direct aseptic collection from the udder through a sterile cannula was used as the reference technique, compared with either a manual or a mechanical sampling method. In this study 30 high-yielding Holstein-Friesian dairy cows at different stages of lactation and free of udder infection were used. For each milk sample, the influence of milk sampling techniques was determined for the following parameters: somatic cell count, milk composition, bacterial contamination, viability, in vitro phagocytosis and overall killing of Staphylococcus aureus Newbould 305, and cellular chemiluminescence. Because milk sampling occurred throughout lactation, the differences between early, mid- and late lactation were estimated. It was concluded that bacterial contamination was not significantly different in manual milking samples and the reference technique; bacterial contamination was, however, significantly (P < 0.001) higher in machine milking samples than in the reference technique. Among the different sampling techniques, no significant effects on SCC, milk composition, viability and functions of the cells isolated from milk were observed. It was found that viability, intracellular killing and cellular chemiluminescence of milk PMN were significantly lower (P < 0.05) in early lactation compared to mid-lactation. Phagocytosis was significantly (P < 0.05) higher in early lactation compared to mid- and late lactation, and no significant differences were observed between mid- and late lactation. From this study, it can be concluded that despite a higher bacterial contamination obtained with the mechanical sampling method, the 3 milk sampling techniques described in this study can be used for the evaluation of milk cell functions.     

Relationship between blood iron parameters and trichinellosis in swine

Reduced levels of total iron binding capacity and unsaturated iron binding capacity were observed in the blood of trichinous and iron-injected trichinous pigs. No change was observed in their serum iron and saturation concentration levels. Also, reduced iron concentration levels were observed in the livers of trichinous pigs, while increased iron concentration levels were observed in the spleens of trichinous pigs and the livers and spleens of iron-injected pigs. No difference was found with regard to weight gains, number of larvae per gram of tissues, or histologic characteristics of 'nurse cells'.     

Salinity Tolerance of Rice (Oryza sativa L.) with Reference to Endogenous and Exogenous Abscisic Acid

Experiments conducted m a phytotron on three rice varieties of different salinity tolerance revealed an increase in the content of endogenous abscisic acid (ABA) with increasing NaCl salinity in IR20 (semi salt-tolerant), but in Pokkali (salt-tolerant) and IR28 (salt-sensitive) the increase in ABA content was marginal. Under sahnity stress, in general, 5 weekly sprayings of ABA (10^-4 mol L^-1) decreased Na and K concentrations in the shoot to the extent of 29.5 % and 3.3 %, respectively. However, ABA application significantly improved the K/Na ratio as well as the chlorophyll fluorescence decrease ratio (Rfd, indicator for potential photosynthetic activity), the number of green leaves per plant and the shoot dry weight. The response of IR20 and IR28 to ABA application was significantly better than that of Pokkali. Increasing salinity caused marked nutrient imbalances, decreased Rfd values and shoot dry weight. The results are discussed in relation to possible mechanism of salinity tolerance.     

Citrullinaemia in Friesian calves

Six Friesian calves from a pedigree herd died or were killed within 1 week of birth because of progressive central nervous disease in which the only consistent lesion was cerebral oedema. The cause was citrullinaemia, resulting from an autosomally inherited dysfunction of the urea cycle enzyme arginosuccinate synthetase. Citrullinaemia was diagnosed by demonstrating markedly elevated concentrations of citrulline in the blood of one calf and in the cerebral spinal fluid of another. One of two sires used in the herd was a heterozygous carrier of the disease. Heterozygocity was demonstrated using a polymerase chain reaction/restriction endonuclease test designed to detect the genetic mutation that causes citrullinaemia in cattle.